Atoms, Molecules, and the States of Matter Chapter 1

1. Atoms, Molecules, and the States of MatterChapter 1

2. Universe Classified • Matter is the part of the universe that has mass and volume • Energy is the part of the universe that has the ability to do work • Chemistry is the study of matter • The properties of different types of matter • The way matter behaves when influenced by other matter and/or energy

3. Elements and Compounds • Substances which can not be broken down into simpler substances by chemical reactions are called elements • Most substances are chemical combinations of elements. These are called compounds. • Compounds are made of elements • Compounds can be broken down into elements • Properties of the compound not related to the properties of the elements that compose it • Same chemical composition at all times

4. Elements • Over 112 known, of which 88 are found in nature • others are man-made • Abundance is the percentage found in nature • oxygen most abundant element (by mass) on earth and in the human body • the abundance and form of an element varies in different parts of the environment • Each element has a unique symbol • The symbol of an element may be one letter or two • if two letters, the second is lower case

6. The periodic table

7. Distribution (Mass Percent) of the 18 Most Abundant Elements in the Earth's Crust, Oceans, and Atmosphere

8. Abundance of elements in the human body

9. Metallic Character • Metalloids • Also known as semi-metals • Show some metal and some nonmetal properties • Nonmetals • brittle in solid state • dull • electrical and thermal insulators • most oxides are acidic and molecular • form anions and polyatomic anions • gain electrons in reactions - reduced • Metals • malleable & ductile • shiny, lustrous • conduct heat and electricity • most oxides basic and ionic • form cations in solution • lose electrons in reactions - oxidized

10. The classification of elements as metals, nonmetals, and metalloids

11. Dalton’s Atomic Theory • Elements are composed of atoms • tiny, hard, unbreakable, spheres • All atoms of a given element are identical • all carbon atoms have the same chemical and physical properties • Atoms of a given element are different from those of any other element • carbon atoms have different chemical and physical properties than sulfur atoms

12. Dalton’s Atomic Theory • Atoms of one element combine with atoms of other elements to form compounds. • Atoms are indivisible in a chemical process. • all atoms present at beginning are present at the end • atoms are not created or destroyed, just rearranged • atoms of one element cannot change into atoms of another element

13. Elements and Compounds • Substances which can not be broken down into simpler substances by chemical reactions are called elements • Most substances are chemical combinations of elements. These are called compounds. • Compounds are made of elements • Compounds can be broken down into elements • Properties of the compound not related to the properties of the elements that compose it • Same chemical composition at all times

14. Formulas Describe Compounds • a compound is a distinct substance that is composed of atoms of two or more elements • describe the compound by describing the number and type of each atom in the simplest unit of the compound • molecules or ions • each element represented by its letter symbol • the number of atoms of each element is written to the right of the element as a subscript • if there is only one atom, the 1 subscript is not written

15. Dalton pictured compounds as collections of atmosphere NO, NO2, and N2O are represented

16. Classification of Matter • Homogeneous = uniform throughout, appears to be one thing • pure substances • solutions (homogeneous mixtures) • Heterogeneous = non-uniform, contains regions with different properties than other regions

17. Pure Substances vs. Mixtures • Pure Substances • All samples have the same physical and chemical properties • Constant Composition  all samples have the same composition • Homogeneous • Separate into components based on chemical properties • Mixtures • Different samples may show different properties • Variable composition • Homogeneous or Heterogeneous • Separate into components based on physical properties • All mixtures are made of pure substances

18. Table salt is stirred into water (left), forming a homogeneous mixture called a solution (right)

19. Sand and water do not mix to form a uniform mixture

20. Identify Each of the following as a Pure Substance, Homogeneous Mixture or Heterogeneous Mixture • Gasoline • a homogenous mixture • A stream with gravel on the bottom • a heterogeneous mixture • Copper metal • A pure substance (all elements are pure substances)

21. Colloids and Emulsions Colloid = mixture of one finely divided material dispersed in another Emulsions = colloids where both compounds are liquids; often commercially useful Ice cream, mayonnaise Emulsifying agent = helps keep two substances from separating (egg yolk keeps water and oil separate in mayonnaise)

22. The organization of matter

23. States of Matter • solid, liquid, gas

24. The three states of water

25. Changes in Matter • Physical Changes are changes to matter that do not result in a change of the fundamental components that make that substance • State Changes – boiling, melting, condensing • Chemical Changes involve a change in the fundamental components of the substance • Produce a new substance • Chemical reaction • Reactants  Products

26. Classify Each of the following as Physical or Chemical Changes • Iron is melted. • Physical change – describes a state change, but the material is still iron • Iron combines with oxygen to form rust. • Chemical change – describes how iron and oxygen react to make a new substance, rust • Sugar ferments to form ethyl alcohol. • Chemical change – describes how sugar forms a new substance (ethyl alcohol)

27. Kinetic - Molecular Theory • The properties of solids, liquids and gases can be explained based on the speed of the molecules and the attractive forces between molecules • In solids, the molecules have no translational freedom, they are held in place by strong attractive forces • May only vibrate

28. Solids • amorphous solids • show no definite structure • therefore strengths of intermolecular forces vary over the structure • glass, plastic, rubber • tend to soften and melt over a temperature range • crystalline solids • orderly, repeating, 3-dimensional pattern • pattern = crystal lattice • melt at one specific temperature

29. The arrangement of sodium ions (Na+) and chloride ions (Cl-) in the sodium chloride, NaCl.

30. Kinetic - Molecular Theory • In liquids, the molecules have some translational freedom, but not enough to escape their attraction for neighboring molecules • They can slide past one another, rotate as well as vibrate • In gases, the molecules have “complete” freedom from each other, they have enough energy to overcome “all” attractive forces

31. Describing a Gas • Gases are composed of tiny particles • The particles are small compared to the average space between them • Assume the molecules do not have volume • Molecules constantly and rapidly moving in a straight line until they bump into each other or the wall • Average kinetic energy proportional to the temperature • Results in gas pressure • Assumed that the gas molecules attraction for each other is negligible

32. Gas Properties Explained • Gases have indefinite shape and volume because the freedom of the molecules allows them to move and fill the container they’re in • Gases are compressible and have low density because of the large spaces between the molecules

33. Gas Pressure • Pressure = total force applied to a certain area • larger force = larger pressure • smaller area = larger pressure • Gas pressure caused by gas molecules colliding with container or surface • More forceful collisions or more frequent collisions mean higher gas pressure

34. The pressure exerted by the gases in the atmosphere can demonstrated by boiling water in a can

35. Liquid Crystals • State of matter intermediate to solid and liquid • Only occurs for a few compounds, usually for molecules that are long and rod-shaped. • The ordered arrangement can be re-ordered by changing the liquid crystal’s environment • Numbers on a digital watch appear as a liquid crystal realigns due to electrical charge and becomes opaque

37. Metallic Mixtures • Alloys are mixtures of elements that show metallic properties • Substitutional Alloys have some host metal atoms replaced by metal atoms of similar size • Brass = Copper with Zinc substituted • Interstitial Alloys have small atoms occupying some of the holes in the crystal lattice of the host metal • Steel = Iron with Carbon added

38. Two types of alloys